Extracellular leucine-rich repeat proteins are required to organize the apical extracellular matrix and maintain epithelial junction integrity in C. elegans

Epithelial cells are linked by apicolateral junctions that are essential for tissue integrity. Epithelial cells also secrete a specialized apical extracellular matrix (ECM) that serves as a protective barrier. Some components of the apical ECM, such as mucins, can influence epithelial junction remodeling and disassembly during epithelial-to-mesenchymal transition (EMT). However, the molecular composition and biological roles of the apical ECM are not well understood. We identified a set of extracellular leucine-rich repeat only (eLRRon) proteins in C. elegans (LET-4 and EGG-6) that are expressed on the apical surfaces of epidermal cells and some tubular epithelia, including the excretory duct and pore. A previously characterized paralog, SYM-1, is also expressed in epidermal cells and secreted into the apical ECM. Related mammalian eLRRon proteins, such as decorin or LRRTM1-3, influence stromal ECM or synaptic junction organization, respectively. Mutants lacking one or more of the C. elegans epithelial eLRRon proteins show multiple defects in apical ECM organization, consistent with these proteins contributing to the embryonic sheath and cuticular ECM. Furthermore, epithelial junctions initially form in the correct locations, but then rupture at the time of cuticle secretion and remodeling of cell-matrix interactions. This work identifies epithelial eLRRon proteins as important components and organizers of the pre-cuticular and cuticular apical ECM, and adds to the small but growing body of evidence linking the apical ECM to epithelial junction stability. We propose that eLRRon-dependent apical ECM organization contributes to cell-cell adhesion and may modulate epithelial junction dynamics in both normal and disease situations.     

Assessing the ecological risks from the persistence and spread of feral populations of insect-resistant transgenic maize

One source of potential harm from the cultivation of transgenic crops is their dispersal, persistence and spread in non-agricultural land. Ecological damage may result from such spread if the abundance of valued species is reduced. The ability of a plant to spread in non-agricultural habitats is called its invasiveness potential. The risks posed by the invasiveness potential of transgenic crops are assessed by comparing in agronomic field trials the phenotypes of the crops with the phenotypes of genetically similar non-transgenic crops known to have low invasiveness potential. If the transgenic and non-transgenic crops are similar in traits believed to control invasiveness potential, it may be concluded that the transgenic crop has low invasiveness potential and poses negligible ecological risk via persistence and spread in non-agricultural habitats. If the phenotype of the transgenic crop is outside the range of the non-transgenic comparators for the traits controlling invasiveness potential, or if the comparative approach is regarded as inadequate for reasons of risk perception or risk communication, experiments that simulate the dispersal of the crop into non-agricultural habitats may be necessary. We describe such an experiment for several commercial insect-resistant transgenic maize events in conditions similar to those found in maize-growing regions of Mexico. As expected from comparative risk assessments, the transgenic maize was found to behave similarly to non-transgenic maize and to be non-invasive. The value of this experiment in assessing and communicating the negligible ecological risk posed by the low invasiveness potential of insect-resistant transgenic maize in Mexico is discussed.     

Evidence of damage from exotic invasive earthworm activity was highly correlated to sugar maple dieback in the Upper Great Lakes region

Sugar maple (Acer sacharrum Marsh.) in the western Upper Great Lakes region has recently been reported with increased crown dieback symptoms, prompting investigation of the dieback etiology across the region. Evaluation of sugar maple dieback from 2009 to 2012 across a 120 plot network in Upper Michigan, northern Wisconsin, and eastern Minnesota has indicated that forest floor disturbance impacts from exotic invasive earthworms was significantly related to maple dieback. Other plot level variables tested showed significant relationships among dieback and increased soil carbon, decreased soil manganese, and reduced herbaceous cover, each of which was also be correlated to earthworm activity. Relationships between possible causal factors and recent growth trends and seedling counts were also examined. Maple regeneration counts were not correlated with the amount of dieback. The recent mean radial increment was significantly correlated with various soil features and nutrients. This study presents significant evidence correlating sugar maple dieback in the western Upper Great Lakes region with earthworm activity, and highlights the need for considering the impacts of non-native earthworm on soil properties when assessing sugar maple health and productivity.     

Prediction of normal values for lactate threshold estimated by gas exchange in men and women

Lactate threshold (LT) is an index of exercise capacity and can be estimated from the gas exchange consequences of a metabolic acidosis (LT_GE). In recent years, it has emerged as a diagnostic tool in the evaluation of subjects with exercise limitation. The purpose of this study was to develop LT_GE prediction equations on a relatively large sample of adults and to cross-validate each equation. A total of 204 healthy, sedentary, nonsmoking subjects (103 men and 101 women), aged 20–70 years, underwent graded exercise testing on a cycle ergometer. The V-slope technique was used to detect LT_GE as the oxygen uptake (V˙O₂) at the breakpoint of the carbon dioxide output versus V˙O₂ relationship. Multiple linear regression was used to develop 12 equations with combinations of the following predictor variables: age, height, body mass, and fat-free mass. Eight of the equations are gender-specific and four are generalized with gender as a dummy variable. The equations were cross-validated using the predicted residual sum of squares (PRESS) method. The results demonstrate that the equations had relatively high multiple correlations (0.577–0.863) and low standard errors of the estimate (0.123–0.228 1 · min⁻¹). The PRESS method demonstrated that the equations are generalizable, i.e., can be used in future studies without a significant loss of accuracy. Since we tested only healthy, sedentary subjects, our equations can be used to predict the lower limit of normal for a given subject. Using individual data for healthy and diseased subjects from the literature, we found that our gender-specific equations rarely miscategorized subjects unless they were obese and mass was a predictor variable. We conclude that our equations provide accurate predictions of normal values for LT_GE and that they are generalizable to other subject populations. Accepted: 13 February 1997     

Genome‐wide SNP identification in Fraxinus linking genetic characteristics to tolerance of Agrilus planipennis

Ash (Fraxinus spp.) is one of the most widely distributed tree genera in North America. Populations of ash in the United States and Canada have been decimated by the introduced pest Agrilus planipennis (Coleoptera: Buprestidae; emerald ash borer), having negative impacts on both forest ecosystems and economic interests. The majority of trees succumb to attack by A. planipennis, but some trees have been found to be tolerant to infestation despite years of exposure. Restriction site‐associated DNA (RAD) sequencing was used to sequence ash individuals, both tolerant and susceptible to A. planipennis attack, in order to identify single nucleotide polymorphism (SNP) patterns related to tolerance and health declines. de novo SNPs were called using SAMtools and, after filtering criteria were implemented, a set of 17,807 SNPs were generated. Principal component analysis (PCA) of SNPs aligned individual trees into clusters related to geography; however, five tolerant trees clustered together despite geographic location. A subset of 32 outlier SNPs identified within this group, as well as a subset of 17 SNPs identified based on vigor rating, are potential candidates for the selection of host tolerance. Understanding the mechanisms of host tolerance through genome‐wide association has the potential to restore populations with cultivars that are able to withstand A. planipennis infestation. This study was successful in using RAD‐sequencing in order to identify SNPs that could contribute to tolerance of A. planipennis. This was a first step toward uncovering the genetic basis for host tolerance to A. planipennis. Future studies are needed to identify the functionality of the loci where these SNPs occur and how they may be related to tolerance of A. planipennis attack.     

Attraction of ambrosia and bark beetles to coast live oaks infected by Phytophthora ramorum

1 Sudden oak death is caused by the apparently introduced oomycete, Phytophthora ramorum. We investigated the role of bark and ambrosia beetles in disease progression in coast live oaks Quercus agrifolia. 2 In two Marin County, California sites, 80 trees were inoculated in July 2002 with P. ramorum and 40 were wounded without inoculation. Half of the trees in each group were sprayed with the insecticide permethrin [cyclopropanecarboxylic acid, 3‐(2,2‐dichloroethenyl)‐2,2‐dimethyl‐(3‐phenoxyphenyl) methyl ester] to prevent ambrosia and bark beetle attacks, and then were sprayed twice per year thereafter. After each treatment, sticky traps were placed on only the permethrin‐treated trees. Beetles were collected periodically in 2003. 3 Inoculated trees accounted for 95% of all beetles trapped. The ambrosia beetles Monarthrum scutellare and Xyleborinus saxeseni and the western oak bark beetle Pseudopityophthorus pubipennis were the most abundant of the seven species trapped. 4 Permethrin treatment delayed initiation of beetle attacks and significantly reduced the mean number of attacks per tree. Beetles did not attack any wounded or noncankered inoculated trees. 5 Trees with larger cankers trapped more beetles early in the disease. Once permethrin lost effectiveness, the number of beetle entrance tunnels was a more reliable predictor of subsequent trap catch than was canker size. 6 Beetles were initially attracted to P. ramorum cankers in response to kairomones generated in the host‐pathogen interaction. After beetles attacked the permethrin‐treated trees, aggregation pheromones most probably were the principal factor in beetle colonization behaviour.     

Synthesis and antiviral evaluation of thieno[3,4-d]pyrimidine C-nucleoside analogues of 2′,3′-dideoxy- and 2′,3′-dideoxy-2′,3′-didehydro-adenosine and -inosine

Several thieno[3,4-d]pyrimidine derivatives, including four hitherto unknown 2′,3′-dideoxy- and 2′,3′-dideoxy-2′,3′-didehydro-C-nucleoside analogues of adenosine and inosine have been synthesized. When evaluated in cell culture experiments against human immunodeficiency virus, none of the tested compounds exhibited any significant antiviral effect, while two of them showed some cytotoxicity.     

Adult spinal opioid receptor μ1 expression after incision is altered by early life repetitive tactile and noxious procedures in rats

Clinical and experimental data suggests that noxious stimulation at critical stages of development results in long‐term changes on nociceptive processing in later life. Here, we use an established, well‐documented rat model of repetitive noxious procedures closely mimicking the clinical situation in the NICU. In order to understand molecular changes underlying the long‐term consequences of repetitive stimulation of the developing nociceptive system the present study aims to analyze the presence of the µ‐opioid‐receptor‐1 (OPRM1). Neonatal rats received either four needle pricks per day in the left hind‐paw from postnatal day 0–7 as a model of procedural pain in infancy. Control pups were handled in the same way but were instead tactile stimulated, or were left undisturbed. At the age of 8 weeks, all animals received an ipsilateral hind‐paw incision as a model for post‐operative pain, and mechanical sensitivity was tested at multiple time‐points. Before, and 1 or 5 days post‐incision, spinal cord tissue was collected for immunostaining of opioid receptor OPRM1. Semi‐quantitative immunocytochemical analysis of superficial laminae in lumbar spinal dorsal horn revealed that: (1) early life repetitive tactile or noxious procedures do not alter baseline levels of OPRM1 staining intensity and (2) early life repetitive tactile or noxious procedures lead to a decrease in OPRM1 staining intensity 5 days after incision in adulthood compared to undisturbed controls. We conclude that early life repetitive tactile or noxious procedures affect the intensity of OPRM1‐immunoreactivity in the lumbar superficial spinal cord dorsal horn after adulthood injury, without affecting baseline intensity. © 2018 The Authors. Developmental Neurobiology Published by Wiley Periodicals, Inc. Develop Neurobiol 78: 417–426, 2018